Refrigerating apparatus



Aug. 18, 1942. s, CRANE 2,293,532

REFRIGERATING APPARATUS Filed .Sept. 29, 1939 2 Sheets-Sheet 1 5 RDOM THERMOSTHT uumwmsa REFRIGE RANT COMPRESSOR IN VENTOR.

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8 8, 1942. R. s. Cl'QANE REFRIGERATING APPARATUS 2 Sheets-Sheet 2 Filed Sept. 29, 1959 WATER P MP WTOR ml m -ROOM g 2 INVENTOR. W 9 m RIR LOHPRESSOR ATTORNEYS.

Patented Aug. 18, 1942 2,293,532 REFRIGERATING APPARATUS Robert S. Crane. Nashville, Tenn, assignor to General Motors Corporation, Dayton, Ohio, a corporation of Delaware Application September 29, 1939, Serial No. 297,168

' 10 Claims. (01. 62-6) This invention relates to refrigerating apparatus and more particularly to apparatus for either heating or cooling a gas by means of a refrigerating system.

One object of this invention is to provide an improved reverse cycle refrigerating system.

Another object of this invention is to provide an improved method of conditioning air.

Still another object of this invention is to provide improved controls for a reverse cycle refrigerating system.

A further object of this invention is to provide controls which prevent functioning of the refrigerating apparatus during the changeover from the one cycle to the other cycle. I

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings, wherein a preferred form of the present invention is clearly shown.

In the drawings:

Fig. l is a diagrammatic view showing the refrigerating apparatus and the air circulating system; and

Fig. 2 is a diagrammatic view showing the electrical control circuits in combination with the pneumatic control system.

In order to simplify the disclosure of the air circulating ducts and the refrigerating system, the controls have been omitted in Fig. l and are shown separately in Fig. 2.

The air flow system For purposes of illustration the air conditioning system has been shown in combination with a plurality of rooms l and I2. It is understood,

ditioned is circulated by means of a central blow- 40 er system l4, which withdraws air from room l0 through the duct l6 and from the room l2 through the duct l8. Air flowing through the ducts l6 and I8 may be mixed with a varying amount of fresh air entering the duct system through the opening 20. The amount of fresh air introduced into the system is controlled by the bellows 24 in a manner to be described more fully hereinafter. The blower system l4 forces the air into the conditioning chamber 26 which is divided into a plurality of airflow passages 28, 36 and 32. In the main passage 28 there is provided a plurality of heat exchange sections 34, 36 and 38 which, -for the purpose of illustration,

discharged into the room ID will have circulated through the heat exchange coils 34, 36 and 38. The damper 40 is also capable of completely closing oil the opening between the duct 44 and the passage 28 whereby all of the air supplied to the room l0 will have been by-passed around the heat exchange coils 34, 36 and 38. With this arrangement. it is possible to independently control the temperature in each of the rooms in a manner to be explained more fully hereinafter.

The recerse cycle refrigerating system The refrigerating system comprises the compressor 48 which discharges compressed refrigerant through the line 50 to the oil separator 52, which may be of any conventional construction. A plurality of valves described hereinafter determine the direction of flow of the refrigerant during each cycle. During the cooling cycle, the compressed gas leaving the oil separator 52 passes through the pipes 54, 5-5 and 51 leading to the heat exchange coil 56. The heat exchanger 56 is arranged within the water tank 58 and functions as a condenser for the compressed refrigerant during the cooling cycle. The condensed refrigerant leaving the heat exchange coil 56 passes through the pipes 64 and 66 leading to the receiver 68.' From the receiver 68 the liquid refrigerant flows through the pipe 16 which sup- :plies liquid refrigerant to the heat exchange coils 34, 36 and 38 via branch pipes 12, 14 and 16. The pipes l2, l4 and 16 are each provided with the usual form of expansion valves 18, 80 and 82 respectively. During the cooling cycle the liquid refrigerant supplied to the heat exchangers 34, 36 and 38 is evaporated therein and returned to the compressor through the suction line 84 in which is .placed a pressure regulating valve 86 of conventional construction and which performs its usual and well-known function. Water is supplied to the tank 58 by means of the water pump driven by the electric motor 62. The water pump 60 may obtain its water from a deep well or any other convenient supply of water. In the have been shown as arranged in series. The 35 event that water from the city water mains is used,'no pump is necessary. While the heat exchanger 56 has been shown as arranged within the water tank 58, it is apparent that certain features of the invention could well be used in combination with a refrigerating system employing an air cooled condenser. Oil separated from the compressed refrigerant in the oil separator 52 returns to the compressor through the oil line 88 leading to the compressor crankcase.

During the heating cycle the system, is valved in the manner explained hereinafter so that the high pressure hot gas discharged from the compressor passes from the oil separator into the pipe line 90 which supplies the hot gaseous refrigerant to the heat exchangers 84 and 36 by way of pipe lines 92 and 94 respectively. The heat exchangers 34 and 36 serve to condense the refrigerant during the heating cycle and the condensed refrigerant returns to the liquid receiver 68 through by-pass lines 120., 14a and the line I0. caused to pass through the expansion valve 98 into the heat exchanger 56 which now functions as an evaporator for cooling the water circulated through the water tank 58. The gaseous refrigerant evaporated in the heat exchanger 56 returns to the compressor through the pipe line 51, valves H and H2, lines I00 and 84. A pressure relief valve I02 is provided in a by-pass I04 which permits refrigerant to be by-passed in the event that the refrigerant pressure becomes excessive.

The control system The control valves which determine the direction of flow and consequently the cycle are all under control of a thermostatic unit generally designated by the reference character H4 and which is located in thermal exchange with the air in any one of the conditioned rooms most representative of the conditions in all of the air conditioned rooms. When the valves I06 and I I0 are open and the valves I01, I08, I09, H6 and H8 are closed, the compressed gas is fed to the heat exchangers 34 and 36 arranged in the path of the cold air whereby heating of the air takes place. When the valves I06, H0 and H2 are closed and valves I01, I08, I09, H6 and H8 are open, then the compressed gas travels to the heat exchanger 56 where it is condensed and the liquid refrigerant thus condensed travels to the heat exchange coils 34, 36 and 38 where it is expanded by the'warm air passing thereover as explained hereinabove. The solenoid valves H6, H8 and I20 are in the closed position during the heating cycle and are used for controlling the amount of cooling during the cooling cycle and are adapted to be controlled by the two-point thermostat generally designated by the reference character I22. The two-point thermostat is of the type in which the temperature responsive element I24, arranged in the path of the air leaving the heat exchangers 34, 36 and 38, actuates a bellows element I26 which operates the valves I28 and I30. The linkage mechanism between the bellows and the valves is so arranged that the one valve operates at a lower temperature than the other valve, for a purpose to be explained more fully hereinafter. When valve I28 is in its uppermost position, air from the bellows. 214 is free to escape through the leak port I29. A similar leak port I3I is provided for the bellows 216.

As explained hereinabove the changeover thermostat I I4 determines whether the apparatus is to heat the air or to cool the air. As shown in Fig. 2, the air pressure used for operating the From the receiver 68 liquid refrigerant isvarious bellows members is supplied by an air compressor I50 driven by an electric motor I52. The air compressed by the compressor I50 discharges into the usual form of compressed air reservoir I54 which communicates with the main air supply line I58 having one branch leading to the constant pressure valve I58 which is set to deliver air at a pressure of 13 lbs. and having another branch leading to the constant pressure valve I60 which is set to deliver air at a pressure of 17 lbs. For purposes of illustration, definite air pressure values and temperature values are referred to throughout the specification, but it is understood that these values are given for purposes of illustration only and that other values may be used by making the necessary adjustments. Air at 13 lbs. pressure is supplied to the chamber I62 provided within the pneumatically operated control valve generally designated by the reference character I64. Air at 17 lbs. pressure is likewise supplied to the chamber I66 in the same valve I64. The controls, as shown in Fig. 2, are set for producing heating and under these conditions air at 13 lbs. pressure is being supplied to the main air line I68 which is provided with a plurality of branches I69, I10, I12, I14, I16 and I18 which lead to the changeover thermostat II4, the pressure operated valve I80, the room thermostat I82, the room thermostat I84, the control I86 and the solenoid operated valve I88 respectively.

The refrigerating system is started by closing the manual switch I90 which energizes the fan motor I92 and thereafter closing the manual switch I94 which is in series with the water pump motor 62. It will be noted from Fig. 2 that the circuit arrangement is such that the water pump cannot be energized unless the air circulating fan I92 is energized since the manual switch I94 is in effect arranged in series with the manual switch I90. The compressor is under control of a first switch I96 forming a part of the pneumatic control element I86 which is responsive to the water temperature in tank 58 and a second switch 200 which is closed by the bellows 202 when the water pressure on the discharge side of the pump is sufficiently high for proper operation. In a typical installation, a water pressure of 25 lbs. has been found to be satisfactory.

In view of the above described arrangement, the compressor motor cannot be started until after the water pump motor has been started which, in turn, cannot be operated until after the main air'circulating fan is in operation.

Upon closing the manual switch I90, a solenoid 204 is energized which controls an air valve I88. Energization of the solenoid 204 opens the valve so that air under pressure in the line I18 is free to flow into the line 206 leading to the damper operating bellows 24. The air pressure in the bellows 24 opens the outside air damper 22. Inasmuch as deenergization of the solenoid coil 204 causes the supply of air to the bellows 24 to be cut off, the outside air damper automatically closes when the air circulating mechanism I4 is stopped. Upon deenergization of the coil 204 the valve I88 closes whereby the air pressure in line 206 gradually drops as a result of leakage of air through the leak port 25. It is to be understood that the outside air damper 22 may be manually adjusted so as to admit the proper amount of air for any particular installation and for any particular condition which may exist. The solenoid valve I 88, when open, also admits air to the air line 208 which supplies air to the valve 2HI which controls the supply of air to the bellows 2I2 and 2I4; the valves 2I6 and 2"; and the humidity control unit 220. The valve 2I0 is provided with a leak port 2H for releasing the air from the main valve chamber. The humidity control unit 220 is so arranged that the humidity responsive element 222 projects into the return air duct adjacent the intake to the blower mechanism as shown in Fig. l. The humidity responsive element 222 actuates the valve arm 224 which cooperates with the leak port 226 and the open.- ing to the air line 228 in communication with the switch operating bellows 238. The arrangement is such that whenever air from the valve 2III is supplied to the humidity control element 220 and humidiiication is required, the valve arm closes the leak port 226 whereby air pressure is supplied to the bellows 230 to close the switch 232 arranged in series with the heating element 234. As shown in Fig. l, the heating element 234 is disposed within a humidifier 236 adapted to contain a constant supply oi? water. humidifier is supplied through the line 238, and the level of water in the humidifier is controlled by a conventional fluid valve 240 which maintains the water level constant. In the event that the addition of moisture to the air is no longer required, the valve-arm 224 moves to a position so as to cut off the supply of air under pressure to the switch operating bellows 230. As'will be pointed out hereinafter, during the summer operating conditions, at which time the addition of moisture is not required, no air under pressure is supplied to the humidity control unit 228 whereby the circuit to the heating coil remains open.

When the control valve 2IIl is in the position shown, air under pressure is supplied to the pneumatically operated valves 2I6 and 2I8 whereby these valves are held open. As shown in Fig. 1. these valves are located in the by-pass lines 12a and 14a respectively whereby the reirigerant flowing from the heat exchangers 34 and 36 is free to flow around the expansion valves I8 and 88. Upon interruption of the suppl of air underpressure to the valves 2I6 and 2I8, these valves automatically close.

As shown in Fig. 2, which illustrates the controls'set for heating, air under pressure from the line 288, enters the bellows 2I2 so as to hold closed the switch 242 which is in circuit with the solenoid valves I86, H2 and H0. These valves are so constructed that, when current is supplied to the valves, the valves are held open. It will also be noted that the solenoid valve IIII is arranged in series with a switch 248 operated by the bellows 256. As shown in Fig. 1, the bellows 258 is responsive to the head pressure at the compressor outlet. In the event that the head pressure becomes excessive during the operation of the refrigerating system, the circuit through the valve IIIl would be interrupted by the switch 248, whereby the valve H8 would automatically close the main suction line to the compressor. By virtue of the control arrangement shown in Fig. 2, the by-pass valve H2 is open at all times during the heating cycle; hence,

when the main suction valve H8 is closed, all of the gas must travel to the compressor through the by-pass valve H2 arranged in the by-pass line H3. A hand valve 244 is arranged in series with valve H2 and is adjusted-to permit the compressor to operate at a reduced head pressure as explained hereinafter. By virtue of the valve I6 and the by-pass line H3 a sufilcient quantity of gas is available at the compressor inlet even Water for the when the valve III! is closed to prevent excessively low pressures at the compressor inlet and to prevent too irequent cycling of the compressor.

In referring to Fig. 2, it is apparent that during the heating cycle air from the valve 2III is also supplied to the bellows 2 which controls the switch 246. When'air under pressure is supplied to the beliows 2l4 the switch 246 is held in the open position whereby the valves I61, I08 and I68 remain closed. However, when the supply of air to the bellows 2 is cut of! the switch 246 closes the circuit to the solenoid valves I01, I88 and I08 whereby these valves are moved to the open position. As will be explained hereinafter, air flows through the valve 2IIl to the bellows 2I2 and 2 during the heating cycle only.

The room thermostats I82 and I84 are located in the rooms in and I2 respectively. These thermostats control the by-pass dampers 48 and 42 respectively which are arranged in the air ducts leading to the respective rooms in which the thermostats are located. These thermostats,

as best shown in Fig. 2, have separate thermoeflective by the air pressure change occasioned l by the changeover thermostat I I4. At a pressure of 13 lbs., the main operating bellows 256 of thermostat I82, for example, causes the needle valve 258 to remain in the position in which it is shown in Fig. 2. A pressure of 17 lbs., such as would be supplied to the bellows 256 during the cooling cycle, would cause the needle valve 258 to move to the right so as to place the supply of air to the damper operating bellows under the control of the thermostatic element 254 rather than under control of the thermostatic element 252. The thermostatic elements 252 and 254 control the supply of air to the damper operating bellows 260 in the conventional and well-known manner which needs no further description.

The purpose of the separate thermostatic elements 252 and 254 is to make the necessary adjustment for the seasonal change in temperature requirements as well as making the necessary adjustment for the change in the air pressure supplied to these control thermostats. The construction and arrangement of the thermostat 252 is such that less air is supplied to the damper operating bellows 268 during the winter season when it is desired to cause a greater amount of air for any one room to flow over the heat exchange coils 34 and 36. Likewise, the construction and operation of the thermostat 254 is such that during the cooling season less air is supplied to the damper operating bellows 268 at such times when a greater amount of cooling is required. The compressor motor is also under the control of the insertion thermostat 262 located near the discharge end of the water tank 58. This thermostat operates the bellows 264 which operates the valve arm 266 so as to close the supply of air to the bellows 268 which holds the switch I86 open in the event that the temperature within the water tank 58 becomes excessively low. It

7 water in the tank 58 drops below 38 F. so as to prevent freezing of the water in the tank 58.

The two-point insertion thermostat I22 located in the conditioned air passage 28 controls the minimum temperature of the conditioned air when the system is functioning as a cooling system. The normally closed switches 218 and 212 are closed when air under pressure is supplied to the operating bellows 214 and 218 respectively. The closing of the switches 210 and 212 opens the valves I20, H8 and H8. The arrangement is such that a drop in temperature below the desired thermostatic setting operates first the one switch 212 and then the other switch 210, first cutting off the supply of refrigerant to the coil 34 by closing the valves H8 and II8 and thereafter closing the valve I20, cutting off the entire supply of refrigerant to all of the coils. During the heating cycle the two-point insertion thermostat is not supplied with air by virtue of the condition in the valve I80 whereby the switches 210 and 212 remain open and the solenoid valves I I8, :8 and I20 remain closed during the heating season.

By virtue of the above described arrangement, it is apparent that each room is separately controlled by its own room thermostat, independent of the main changeover thermostat I I4 which determines the cycles by varying the amount of air which is permitted to escape through the opening II1. As the temperature in the respective rooms rises during the heating cycle, the room thermostats begin to close off their respective dampers to the air leaving the heatexchange coils and allow a greater volume of air to bypass the coils. Thus, the condensing effect of the heat exchangers located in the air stream is decreased and the condensing pressure increases because of the lessening of the heating demand. Upon a continuation of this increase in condensing pressure the switch 248 controlling the valve IIO opens, thereby allowing the valve IIO to close the main suction line to the compressor. The decrease in the amount of gas available for compressor suction reduces the condensing pressure, whereby at a lower pressure the valve H is reopened. This action may occur frequently when the demand for heating is very nearly satisfied and will continue until the main thermostat II4 stops the operation of the system. The valve I I2 arranged in the by-pass around the valve IIO operates simultaneously with the operation of valve I06 so that a sufilcient amount of gas is available at the compressor inlet to prevent immediate pumpdown to a vacuum and subsequent short-cycling at such times when the solenoid valve I I0 is closed due to the high condensing pressure. The amount of gas passing through the valve I I2 is controlled as explained hereinabove by operation of the hand valve 244 arranged in series with the valve H2.

The changeover thermostat II4 controls the changing over from heating to cooling and vice versa by varying the air pressure supplied to the pneumatically operated control valve I80. Preferably, thechangeover thermostat is adjusted so as to cause a change of approximately 2 lbs. in the air pressure in line I I5 per degree of temperature change. Thus, it may be said to start to act at a temperature of 72 F., and at 74 F. it has built up a pressure of 4 lbs. on the branch line leading to the control valve I80. This 4-lb. pressure, however, is insufiicient to change the valve from the position in which it is shown in Fig. 2. Air at this same pressure is also supplied to the bellows 280 and the bellows 282. The bellows 280 operates the switch 284 which is arranged in series with the switch controlling the water pump. The bellows 280 is adapted to open the switch 284 when the pressure supplied to the bellows reaches the 8-lb. value. However, the bellows 282 which operates the switch 288 is adapted to close the switch 286 when the pressure supplied to the bellows reaches a value of 12 lbs. By virtue of this arrangement, whenever pressures between 4 lbs., which corresponds to a temperature of approximately 74 F., and 12 lbs., which corresponds to a temperature of approximately 78 F., the water pump starter circuit is open resulting in an 011" cycle of the compressor and water pump. The values of 74 F. and 78 F. have been given for purposes of illustration, and it is presumed that between these temperatures neither heating nor cooling is required in any of the rooms.

As the temperature at the changeover thermostat II4 rises from 74 F. to 75 F. the resulting branch line air pressure supplied to the operating bellows I8I for the valve I80 operates the valve so that air under pressure of 13 lbs. supplied through the pipe I10 is also supplied through the pipe I1I leading to the bellows element I 65 which operates the valve I84 so as to close off the air at 13 lbs. pressure and open the passage from the valve I60 which supplies air at 17 lbs. pressure to the main air line I88. This change in pressure supplied causes the valve 2I0 to cut off the supply of air from the line 208 to the bellows which operate the switches 242 and 246 and also renders inoperative the humidostat 220 so that during the cooling cycle no moisture is added to the air being conditioned. As a result of this change in pressure, the switch 242 assumes its normally open position, thereby cutting off the current to the solenoid operated valves I06, H0 and H2. Likewise, the normally closed switch 246 moves to closed position, thereby energizing the solenoid valves I01, I08 and I09 so as to open these valves. Upon valve 2) closing, the supply of air to the valves 2I8 and 2 I8 is also cut 011, thereby closing said valves so as to prevent the refrigerant from by-passing the expansion valves 18 and 80.

As pointed out hereinabove, the increase in the air pressure from 13 lbs. to 17 lbs. in the main air line I88 resets the room thermostats I 82 and I84 so as to properly operate at the 17-lb. air pressure so as to maintain proper temperatures during the cooling cycle. The thermostat I24 arranged on the discharge side of the heat exchangers 34, 38 and 38 is also supplied with air from the valve I80 so as to supply the necessary air pressure for proper operation of the pneumatically operated switches 210 and 212. As pointed out hereinabove, these switches control the flow of refrigerant to the heat exchange coils 34, 36 and 38 which now function as evaporator coils.

It will be noted that, by virtue of the above described control system, all of the above valve operation, except that of the suction line control solenoid valve IIO, occurs on air pressures from the changeover thermostat II4 between approximately 4 lbs. and 12 lbs., during which interval the water pump and compressor are inoperative; and regardless of whether the temperature is rising or falling, an air pressure of 8 lbs. in the branch line II5 leading from the changeover thermostat II4 will reset the valves which control the next cycle and do this during a period of off cycle for the water pump and compressor.

While the form of embodiment of the invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

said first heat exchange means, means for by-:

passing at least a portion of said gas around said first heat exchange means, means responsive to one function of the psychrometric condition of said gas for controlling said by-pass means, means for varying the capacity of said compressor, means for flowing a fluid over said secand heat exchange means, means preventing the operation of sa compressor when said fluid flowing means ineffective, a changeover thermost-at for changing over from the heating cycle to the cooling cycle, and means for preventing operation of the compressor during changeover from the heatingcycle to the cooling cycle.

2. In a reverse cycle refrigerating system,v a first heat exchange means, a second heat exchange means, a compressor for withdrawing refrigerant vapor from one of said heat' exchange to one function of the psychrometric condition of said gas for controlling said lay-pass means, means for varying the capacity of said compressor, means for flowing a fluid over said second heat exchange means, means preventing the operation of said compressor upon failure of said fluid flowing means, a changeover thermostat for changing over from the heating cycle to the cooling cycle, and means for preventing operation of the compressor during changeover from the heating cycle to the cooling cycle, said last named means comprising means for controlling the flow of fluid over said second heat exchange means.

3. In a reverse cycle refrigerating system, a

compressor, first and second heat exchange.

units, refrigerant flow connections between said compressor and said first and second heat exchange units, said fluid-flow connections including a refrigerant line from one of said units to said compressor, a valve in said line, means responsive to high condensing pressure for'closing said valve, means for by-passing said valve, and means for controlling the flow of refrigerant through said by-pass.

4. Air conditioning apparatus comprising, in-

combination, a compressor, complementary heat exchange units, fluid-flow connections between said compressor and said units, means for reversing the functions of said complementary heat heat exchangers, means for circulating a gas to be conditioned over one of said heat exchangers, 1s

ahd means for lay-passing at least a portion of d gas around said heat exchanger, means for varying the capacity of said compressor so as to compensate for changes in the load on said compressor, and means for rendering one portion of oneof said heat exchangers ineffective during 'onecycle of operation,

6. In a reverse cycle refrigerating system for conditioning air for a plurality of enclosures, a compressor, a pair of complementary heat exchangers, refrigerant flow connections between said compressor and said heat exchangers, means for circulating air to be conditioned for said enclosure in thermal exchange with one of said heat exchangers, means for circulating an ex-\ traneous medium over the other of said heat exchangers, a separate duct for supplying conditioned air to each of said rooms, a separate bypass for by-passing air for each separate room around said one heat exchanger,'means for reversing the heating and cooling functions of said heat exchangers, and means for reducing the capacity of said compressor so as to compensate for changes in the load on said compressor.

7. In combination, a reverse cycle'refrigerating system comprising a compressor and a plurality of heat exchange coils arranged in refrigerant flow relationship, means for flowing air for a plurality of rooms in thermal exchange relationship with one of said coils, means for bypassing air for said rooms around said one coil, independent means for varying the effective surface of said one coil, and means for unloading said compressor when the load on said compressor exceeds a predetermined value such as results when a major portion of the air by-passes said one coil.

8. In combination, a first heat exchange means, a second heat exchange means, a compressor for withdrawing refrigerant from one of said heat exchange means and discharge ing, compressed refrigerant into the other of said heat exchange means, means for circulating a gas to be conditioned over said first heat exchange means, means to circulate a fluid over said second heat exchange means, control means for operating said refrigerating system so as to heat said gas throughout a predetermined low temperature range and for operating said refrigerating system to cool said gas throughout a predetermined high temperature range, said control means including means for automatically increasing the effective heat transfer surface of one of said heat exchange means inresponse to changing over from heating to cooling.

9. Air conditioning apparatus comprising in combination, a pair of complementary heat exchange units, a refrigerant compressor withdrawing refrigerant vapor from one of said units and discharging compressed refrigerant vapor into the other of said units whereby one of said units serves as an evaporator and the other of said units serves as a condenser, means for reversing the functions of said complementary heat exchange units, one of said units comprising a pluralityof sections, means for preventing the flow of refrigerant through one of said sections when heating of the air is required, and means for bypassing air around said sections in response to changes in the requirements for conditioned air.

10. In combination, an air conditioning chamber, means for circulating air tobe'conditioned through said chamber, means for cooling the air flowing through said chamber, means for discharging the air leaving said chamber into a plurality of rooms to be conditioned, means for introducing fresh air into said chamber, means for controlling the introduction of fresh air to said chamber,'means for returning air-from each or said rooms to said chamber, means for by-passing a variable amount of air for one of said rooms 5 ing means. t

around said air cooling means in response to changes in the temperature within said one room, and means responsive to the temperature in another of said rooms for controlling said air cool- ROBERTS. CRANE. 

